The present invention generally relates to sealing devices and methods and, more particularly, to improved sealing devices and methods which are especially adapted for sealing piston and cylinder assemblies and the like. In this regard, an important embodiment of the present invention is directed to an improved sealing assembly and method wherein a circumferentially compressed stepped joint piston ring and expander are positioned within an annular groove in a piston employed in high pressure hydraulic applications.
Piston ring and expander combinations have heretofore been employed as sealing devices in piston and cylinder assemblies used in a wide variety of applications. In general, it has been found advantageous to manufacture these rings of one-piece, substantially rigid construction with a split therein so as to facilitate their installation in a groove in the piston in overlying relation with the expander.
Heretofore, many of these split piston rings have been composed of a wide variety of materials including synthetic resins and have been characterized by a so-called stepped joint construction; that is, one wherein the ring ends are stepped and overlay one another. In accordance with previously employed techniques, these rings were manufactured with a gap or circumferential spacing in their pre-installed condition which was expected to close or substantially close when the ring was fully installed within the bore of the cylinder in overlying relation with the elastomeric expander in a groove in the piston.
Experience with these synthetic resin stepped joint piston ring and elastomer expanders, however, has indicated a higher failure rate than was originally anticipated. In this regard, it was found that upon installation in the cylinder bore, a gap was present, resulting in nibbling or extrusion of the elastomeric expander into the gap and producing a failure of the seal assembly. It is believed that this problem has been caused, at least in part, by frictional forces present between the expander and ring, when installed, which have prevented circumferential travel of the ring ends to the extent necessary to close or at least substantially close the gap.
In accordance with the present invention, the foregoing problems and disadvantages of these stepped joint piston ring and expander sealing devices have been overcome through the use of stepped joint piston rings composed of a circumferentially compressible synthetic resin in an oversized closed gap condition; that is, one wherein prior to final installation in the cylinder bore, the ring ends are in contact with each other, or at least in very close spacial relation from each other. Installation of these rings within the bore of a cylinder is accomodated by reason of the compression of the ring itself. As such, the practice of the present invention has resulted in the elimination of a gap in which the elastomeric oval expander can extrude into or nibble on and, at the same time, has produced increased circumferential pressure of the ring thereby substantially improving the effectiveness of the seal ring within the cylinder bore.
An object of this invention is to provide an improved seal assembly and method.
Another object of the present invention is an improved seal assembly and method that is especially suitable for use in an annular groove in a piston employed in high pressure applications.
Another object of the present invention is to provide a split seal ring in combination with a resilient expander wherein the split seal ring is manufactured with an oversized closed gap condition and is itself circumferentially compressed when installed between the surfaces to be sealed.
Another object of the invention is an improved ring used in combination with a resilient expander ring, which improved ring has an oversized closed stepped joint gap condition and further has a modulus of elasticity which combine to allow for circumferential compression of the ring upon installation.
Another object of the invention is an improved piston, cylinder and seal assembly especially suitable for hydraulic applications, which assembly includes a resilient expander positioned in combination with a split, one-piece piston ring that has an oversized closed gap condition and is circumferentially compressed when installed.
Another object of the invention is an improved method for sealing opposing, reciprocating surfaces by circumferentially compressing a sealing member having an oversized closed gap condition between said opposed surfaces to the extent that the sealing member remains in closed gap condition during reciprocation of the opposed, sealed surfaces.